1. Field of the Invention
The present invention relates to a structure of a lens-shutter device incorporating a plurality of sectors.
2. Description of the Related Art
A conventional type of diaphragm for varying an aperture for photographic light transmission, which is incorporated into cameras and so forth, is disclosed in Japanese Unexamined Patent Publication No. 63-19636. Such a diaphragm is equipped with aperture blades that are disposed on the base in such a manner that they can slide, in which a lifting-prevention member for preventing the aperture blades from lifting from the base is disposed integrally with the base. The aperture blades slide, in the area in which a shutter of the device opens and closes, making linear contact with the lifting-prevention member. Such sliding enables satisfactory shielding to be obtained.
However, in the above-mentioned device, which is disclosed in Japanese Unexamined Patent Publication No. 63-19636, the aperture blades are arranged in a manner in which they slide making linear contact with the lifting-prevention member while an equal gap is maintained between them from the open state to the closed state of the aperture. As a result, in the opening and closing action of the shutter, a relatively large drive load is necessary. Thus, in the device disclosed above, there is no consideration for reduction in the drive load and for effective prevention of light from leaking in the closed state of the shutter.
As for a conventional type of shutter device operated by means of opening and closing an aperture through which photographic light passes, there is a lens-shutter device arranged with four blades. This type, with an increased number of blades, has smaller blades and a minimized projected area of the shutter.
Such a lens-shutter device arranged with four blades needs equal gaps between the blades in the direction of the optical axis depending on the number of blades, since it has multiple blades. Consequently, a relatively large gap may be created by an unbalanced leaning position of the four blades in the direction of the optical axis when the shutter is closed, and, thus, light easily leaks through the gap.